The present invention refers to a device for chopping straw of the type which comprises a rotor arranged in an apparatus housing, said rotor having knife arms projecting radially therefrom, which when rotated pass between a number of counter-knives, located in a row and attached to a knife beam, the knife arms and counter-knives being produced of flat bars provided with at least one sharpened edge on one of its long sides.
The Swedish patent publication no. 403.552 (corresponding to German patent no. 2.801.827) describes a device of the above mentioned type, where every knife arm presents a double cutting surface along both long sides. A knife which has been damaged on the cutting edge can thereby be used again by turning the other edge-provided side to an active position. The production cost for a knife of this type is relatively high due to the number of sharpening steps needed.
Tests have been carried out to improve the cutting result of the straw chopper by arranging the knives closer to each other. This has not given the desired effect but has instead resulted in an increased power consumption.